The present invention generally relates to complex shaped articles and a method for manufacturing such articles. Illustrative of such complex shaped articles are aerodynamic airfoils (e.g., wings, rudders, elevators, and the like for use on planes, air ships, space vessels, and the like), hydrodynamic airfoils (e.g., ship rudders, ship stabilizers, sail boat keels, and the like), and other airfoil articles such as aquatic sports boards (e.g., surfboards, sailboards, water skis, and the like).
These complex shaped articles have generally followed similar, parallel routes in the evolution of their development and improvement; namely, lighter, more durable articles having complex shapes designed to perform in a selected environment. The development and improvement of such complex shaped articles can be traced through an aquatic sports board such as a surf board which presents a common background for and is exemplary of other types of complex shaped articles mentioned above; i.e., aerodynamic air foils and hydrodynamic air foils. The ensuing description of the invention, therefor, should be understood as being only exemplary and illustrative of these other types of complex shaped articles.
Riding a board on the crest of a wave as it approaches the shore dates back to at least the eighteenth century when European sailors documented the feat in the Sandwich Islands. The sport spread from Hawaii to California, Australia, South Africa and around the world in the twentieth century. As the sport was introduced around the world, the surfboards used were heavy, curvilinear artifacts measuring from twelve to twenty feet in length so that only the strongest surfers could handle them. With the advent of new technologies, construction techniques, and materials, the sport has grown in popularity and surfing enthusiasts have placed increasing demands on performance, maneuverability, speed, durability, weight and size.
Typical, commercially available surfboards are constructed from a core of foam or honeycomb material which is encased in a protective layer of reinforced resin and which usually include fins on their bottom surface to impart stability and control. These surfboards generally have curved profiles which aid a rider in maintaining fore and aft as well as side to side balance and which approximates the curvature of the forward slope of a wave. In efforts to improve their performance, aquatic sports boards have been produced having a variety of configurations and shapes. Fins have been added to provide stability and further improve performance and different types of materials have been used for their fabrication. Manufacturing techniques for such aquatic sports boards have generally required the use of complex molds, processes and tooling.
Surfboard riders generally desire a surfboard that will readily enable the user to attain maximum maneuverability within a wide range of speeds and to achieve the maximum speed possible for best overall performance. Maneuverability is governed primarily by the shape and the weight distribution of the surfboard which is typically augmented by the addition of one or more specially shaped fins on its underside. Weight is an important consideration in achieving maneuverability as minimum weight is a key factor in achieving the maximum speed possible for a specific surfboard design. Durability, resistance to damage, structural integrity, long term usability and appearance are other important requirements for the user and depend upon construction materials, manufacturing techniques and construction and structural design.
The development of and improvements to surfboards have been directed toward their construction, shape, maneuverability, speed, and decreased weight, but the combination of high performance, minimum weight, durability and attractive appearance have been difficult to obtain or have been unattainable. A simple method for their manufacture has been equally elusive.
Many attempts have been made to decrease the weight and improve the performance, construction and durability of aquatic sports boards. The literature for aquatic sports boards have described the use of honeycomb material, foam and other similar materials for their construction. Attempts to manufacture such aquatic sports boards have generally required the use of complex and costly molds, processes and tooling. Consequently, there still remains a need for light weight, high strength aquatic sports boards that will have long term durability, a high degree of maneuverability, an attractive appearance and that are easy and inexpensive to manufacture and that do not require complex molds, processes or tooling for their manufacture.
Surfboards having foam cores have been attempted. For example, U.S. Pat. No. 3,160,987 to Kelly, Jr. discloses a hydroplane surfboard fabricated from a fiberglass covered, air expanded plastic foam or balsam wood. The surfboard has a planing surface and a scorpion tail so that a rider, by body movement or shift in weight, can bring the planing surface into partial or full play or induce drag thereby achieving a wide range of speeds while maintaining maneuverability during surfing.
U.S. Pat. No. 4,713,032 and its divisional U.S. Pat. No. 4,806,302 both to Frank disclosed a method for manufacturing surfboards and sail boards in which a prefabricated foam core has fibrous material wound about it. A resin such as polyurethane is especially set with a reaction retarder and poured onto the fibrous material whereupon the foam core is then inserted into a molding tool and the mold is closed to cure the resin.
U.S. Pat. No. 3,543,315 to Hoffman discloses a soft board fabrication in which a surfboard with a low density core is provided with a skin of depressible material. The core can be constructed from a phenolic impregnated paper honeycomb material.
U.S. Pat. No. 5,145,430 to Keys, et.al. discloses a surf craft such as a surfboard or windsurfer having a planing plank with a stiffening spine integral with the planing plank to impart additional strength and flexibility. The surf craft has a sandwich construction with a core of foam material encased by a shell of fiber reinforced resin.
Hollow surfboards and sail boards have also been attempted. For example, U.S. Pat. No. 3,514,798 to Ellis discloses a surfboard with an outer shell or skin of solidified laminating polyester resin adhered to a sheet of honeycomb material and a longitudinal cavity within the surfboard. A sheet of glass cloth is pressed onto the outer shell or skin of solidified laminating polyester resin while the resin is still moist and it is then impregnated with the same resin while in a mold. The mold consists of two halves having the configuration of the surfboard when the mold is closed. The moist outer shell is pressed onto the honeycomb material which is then impregnated with a thermosetting phenolic resin and secured by adhesion. The resulting structure includes considerable air space within the body of the surfboard.
U.S. Pat. No. 4,964,825 to Paccoret discloses an aquatic board construction for surfboards and sail boards in which shaped upper and lower sections are joined together to form a board with a generally hollow interior. Each section is formed with a generally sandwich construction including a high strength outer skin, an inner skin spaced from the outer skin, and a core formed from filler material which is sandwiched between the inner and outer skins. The inner and outer skins can be formed from one or more layers of a cured thermosetting resin which has been impregnated into a fabric material. The core can be provided from a foam or honeycomb material.
U.S. Pat. No. 5,266,249 to Grimes III, et.al. discloses a method of forming a hollow, fiber reinforced plastic structure, such as the hull of a sail board, from a fiber reinforced plastic material in a female mold.
Foam filled honeycomb and foam filled plastic objects are also of interest.
For example, U.S. Pat. No. 4,797,312 to Sherwood discloses a foam-honeycomb article and method for its manufacture wherein expanded foam in the cells of a multi-cell honeycomb material braces the honeycomb side walls against collapse to increase the strength and rigidity of the article.
U.S. Pat. No. 4,383,955 to Rubio discloses a process for fabricating hollow, foam filled, reinforced plastic objects such as surfboards using a multi-part mold.
U.S. Pat. No. 4,510,105 to Sherwood discloses a method for molding an article having a core of foam and a surface reinforced by fiberglass clothe which can be used as a surfboard.
Foam filled honeycomb core skis and honeycomb core skis have been disclosed.
For example, U.S. Pat. No. 3,276,784 to Anderson discloses a laminated snow ski having a foam filled honeycomb core. The ski construction is composed of a molded, elongated, resin impregnated fiberglass outer shell and a foam filled aluminum honeycomb core integrally bonded to the interior surfaces of the fiberglass outer shell.
U.S. Pat. No. 3,734,519 to Bennett discloses a one shot molded ski having cored recesses at right angles to the general plane of the ski.
U.S. Pat. No. 3,201,138 to Brown, Jr. discloses a laminated ski construction with a cellular honeycomb core.
U.S. Pat. No. 5,183,618 to Pascal, et.al. discloses a process for manufacturing a ski whose body includes a core covered with a shell and which is fabricated in a mold cavity. The core can include a synthetic foam or aluminum honeycomb.
As can be seen from the foregoing, efforts have been made towards construction, shape, maneuverability, increased speed and decreased weight. However, the combination of high performance, minimum weight, durability and attractive appearance have been difficult to achieve or unattainable, especially for aquatic sports boards. Attempts to manufacture such aquatic sports boards have generally required complex molds, processes and tooling. Honeycomb core shaping, for example, is typically performed on a five axis milling machine in order to obtain the complex shapes necessary for contouring aquatic sports boards. Such milling machines normally remove material measuring approximately 2.0xe2x80x3 by 0.40xe2x80x3 at a rate of about 300 linear inches of material per minute consuming about one hour to shape one side of a typical aquatic sports board. Most of the known aquatic sports boards are too heavy to achieve the highest speeds and optimum performance possible while retaining long term durability and an attractive appearance. A typical xe2x80x9clight weightxe2x80x9d aquatic sports board currently available weighs about 5.4 pounds.
For the foregoing reasons, it would be desirable to provide an aquatic sports board that is lighter in weight, has high strength, provides long term durability, has a high degree of maneuverability and an attractive appearance, is easy and inexpensive to manufacture, and which does not require complex molds, processes, or costly tooling for its manufacture.
As mentioned earlier, the foregoing discussion relating to aquatic sports boards and their manufacture is equally applicable to the other types of complex shaped articles described hereinabove; i.e., aerodynamic air foils, hydrodynamic air foils and other air foil articles.
The present invention is directed to complex shaped articles and a method for manufacturing light weight, high strength complex shaped articles having long term durability and a high degree of maneuverability that is simple, easy and inexpensive, does not require complex molds, processes or tooling, and that will result in a significant reduction in weight of such complex shaped articles.
Features of the invention include a one piece honeycomb core conformably shaped for dynamic movement, formed edges, and an outer skin having at least one layer of fiber reinforced resin adjoined to the honeycomb core for protecting and encasing the honeycomb core and to provide a drag resistant surface.
In general, the method for manufacturing the complex shaped articles of the invention comprises: trimming, cutting and shaping a core to a desired size and shape; deforming said core; permanently setting the shape and contour of said core; affixing edges to said core; and, affixing at least one layer of fiber reinforced resin to the top and bottom surfaces of said core.
Illustrative and exemplary of the complex shaped articles that can be provided according to the present invention are:
An article having a contoured arc extending along its longitudinal axis from the front end to the rear end of said article and a contoured arc extending across its transverse axis between the opposed sides of said article such that a concave, symmetrical contour is defined on the upper surface of said article and a convex, symmetrical contour is defined on the lower surface of said article.
Articles having this type of complex shape can be used for aquatic sports boards such as surfboards and sail boards. When grooves are added to their bottom, contact surfaces and their forward ends are turned upwardly, such articles can be used as snow skis, water skis, hydroplanes, and the like.
An article having a contoured, arcuate shape on one surface thereof extending across its transverse axis between the opposed sides of said article and extending along its longitudinal axis from one end to the other of said article such that a convex, symmetrical arc is defined between said opposed sides on one surface of said article, said convex arc being significantly higher at one of said opposed sides and tapering therefrom across said transverse axis and along said longitudinal axis to a significantly lower height at the other of said opposed sides.
Articles having this type of complex shape can be used as aerodynamic air foils such as wings and elevators for air planes, air ships, space vessels, and the like, as well as hydrodynamic air foils such as stabilizers for ships.
Articles having a symmetrical, contoured arcuate shape on both planar surfaces of said article extending across the transverse axis of each planar surface between the opposed sides of said article and extending along the longitudinal axis from one end to the other on each planar surface of said article such that a symmetrical, convex arc is defined between said opposed sides along said longitudinal axis on each of said planar surfaces, said convex arc being significantly higher at one of said opposed sides on each of said planar surfaces and tapering therefrom across said transverse axis of each of said planar surfaces and along said longitudinal axis to a significantly lower height at the other of said opposed sides.
Articles having this type of complex shape can be used as aerodynamic air foils such as wings, rudders and elevators of air planes, air ships, space vessels, and the like, as well as hydrodynamic air foils such as rudders, stabilizers, keels, and the like for ships and sailing vessels.